http://jslhr.pubs.asha.org/article.aspx?articleid=1774169Factors Affecting the Benefits of High-Frequency AmplificationPurpose:
This study was designed to determine the extent to which high-frequency amplification helped or hindered speech recognition as a function of hearing loss, gain-frequency response, and background noise.Method:
Speech recognition was measured monaurally under headphones for nonsense syllables low-pass filtered in one-third-octave steps between 2.2 and 5.6 ...2008-06-01T00:00:00Article/ReportAmy R. Horwitz

Purpose:
This study was designed to determine the extent to which high-frequency amplification helped or hindered speech recognition as a function of hearing loss, gain-frequency response, and background noise.

Method:
Speech recognition was measured monaurally under headphones for nonsense syllables low-pass filtered in one-third-octave steps between 2.2 and 5.6 kHz. Adults with normal hearing and with high-frequency thresholds ranging from 40 to 80 dB HL listened to speech in quiet processed with an identical “nonindividualized” gain-frequency response. Hearing-impaired participants also listened to speech in quiet and noise processed with gain-frequency responses individually prescribed according to the National Acoustic Laboratories–Revised (NAL-R) formula.

Results:
Mean speech recognition generally increased significantly with additional high-frequency speech bands. The one exception was that hearing-impaired participants’ recognition of speech processed by the nonindividualized response did not improve significantly with the addition of the highest frequency band. Significantly larger increases in scores with increasing bandwidth were observed for speech in noise than quiet.

Conclusions:
Given that decreases in scores with additional high-frequency speech bands for individual participants were relatively small and few and did not increase with quiet thresholds, no evidence of a degree of hearing loss was found above which it was counterproductive to provide amplification.

Acknowledgments

This work was supported (in part) by research grants K23 DC00158, P50 DC00422, and R01 DC00184 from the National Institute on Deafness and Other Communication Disorders and by Grant M01 RR01070 from the Medical University of South Carolina General Clinical Research Center. This investigation was conducted in a facility constructed with support from Research Facilities Improvement Program Grant Number C06 RR14516 from the National Center for Research Resources, National Institutes of Health. Helpful contributions from Fu-Shing Lee, Rebecca McDonald, Stefanie R. Reed, and Jillanne Schulte are gratefully acknowledged.

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